Ironing appliance comprising a safety device and method of making an ironing appliance safe.

ABSTRACT

Ironing appliance comprising a heating element ( 1 ) controlled by means of a thermostat ( 2 ), the appliance having a safety device comprising motion detection means ( 5 ) and a safety relay ( 3 ) connected in series with the heating element ( 1 ) to interrupt the supply to said heating element ( 1 ) when the appliance is left stationary for too long, said appliance being characterized in that said safety device comprises means ( 2   a ) for determining the state of opening of the thermostat ( 2 ) and in that the safety device opens said safety relay ( 3 ) when, simultaneously, the determining means ( 2   a ) indicate that the thermostat ( 2 ) is open and the motion detection means ( 5 ) detect that the appliance has not been moved for a time t greater than a warning threshold t 1 .

The present invention relates to an ironing appliance composed of aheating element controlled by means of a thermostat and moreparticularly to an appliance provided with a safety device comprisingmeans for detection of movement and a relay assembled in series with theheating element so as to interrupt the supply of power to the heatingelement when the appliance remains motionless for too long a time.

There is known, from the U.S. Pat. No. 4,661,685, a domestic ironcomposed of a heating element and a safety device controlling theopening of a relay assembled in series with the heating element tointerrupt the supply of power to the latter when the iron remainsmotionless too long on its soleplate. This safety device alsocontributes to limit the electric consumption of the iron by stoppingthe power supply when the iron remains motionless too long on its heel.

Such a safety device controls the opening of the relay only according tothe time during which the iron is motionless, or immobile, so that theopening of the relay is generally carried out when current for supplyingthe heating element passes through the relay. The relay must thus bedimensioned to support a large number of openings while it is beingsupplied with voltage, which leads to choosing a relay that is expensiveto manufacture.

The invention which follows aims at providing an ironing appliancecomposed of a safety device that is more economical to implement. Theinvention in particular aims at providing a safety method for a domesticiron that makes it possible to use a safety relay that is less expensiveto manufacture.

The goal of the invention is reached by an ironing appliance composed ofa heating element controlled by means of a thermostat, the appliancebeing provided with a safety device comprising means for detection ofmovement and a safety relay mounted in series with the heating elementmaking it possible to interrupt the supply of power to the heatingelement when the appliance remains motionless too long, wherein thesafety device is composed of means for determining the opening state ofthe thermostat and the safety device controls the opening of the safetyrelay when, simultaneously, the means for determining indicate that thethermostat is open and the means for detection of movement detect animmobilization of the appliance during a time t longer than an alarmthreshold t₁.

Such a characteristic makes it possible to control the opening of thesafety relay when current is not flowing through the latter so that wearof the safety relay is greatly reduced.

According to another characteristic of the invention, the safety devicecontrols, at the latest, the opening of the safety relay when theappliance is motionless during a time t longer than a critical thresholdt₂, the critical threshold t₂ being longer than the alarm threshold t₁.

Such a characteristic makes it possible to ensure maximum safety byensuring cutting of the power to the heating element when the timeduring which the appliance is motionless exceeds the critical thresholdt₂.

According to another characteristic of the invention, the safety devicemonitors the state of the thermostat when the time during which theappliance is motionless is comprised between the alarm threshold t₁ andthe critical threshold t₂ and controls the opening of the safety relayas soon as the thermostat is detected to be in an open state by themeans for determining the state of opening.

According to still another characteristic of the invention, theappliance comprises a heel on which it can rest at the time of theinactive phases of ironing and an ironing soleplate, in thermalcommunication with the heating element, on which it can rest for theactive phases of ironing, the appliance comprising position detectingmeans making it possible to determine if the appliance rests or not onits heel and the values of the alarm threshold t₁ and the criticalthreshold t₂ are a function of the position of the iron detected by theposition detecting means.

According to another characteristic of the invention, the values of thealarm threshold t_(1r) and critical threshold t_(2r) when the iron restson its heel are respectively longer than the values of the alarmthreshold t_(1s) and critical threshold t_(2s) when the appliance restson its soleplate.

The invention also relates to a safety method for an ironing applianceprovided with a heating element controlled by means of a thermostat inwhich a safety relay, disposed in series with the heating element, isopen when the appliance remains motionless too long, wherein the safetyrelay is open when the thermostat is in an open state and the applianceis motionless during a time t longer than an alarm threshold t₁.

According to another characteristic of the invention, the safety relayis opened, at the latest, when the appliance is motionless during a timet longer than a critical threshold t₂, the critical threshold t₂ beinglonger than the alarm threshold t₁.

According to another characteristic of the invention, the state ofopening of the thermostat is monitored over a time period ofimmobilization of the appliance ranging between the alarm threshold t₁and the critical threshold t₂ and the safety relay is opened as soon asthe thermostat is detected in an open state in the immobilization timeperiod.

One will better understand the goals, aspects and advantages of thepresent invention, from the description given hereafter of a particularembodiment of the invention, presented as a non-limiting example, whilereferring to the annexed drawings in which:

FIG. 1 is a schematic representation of the supply circuit for theheating element of a domestic iron according to a particular embodimentof the invention;

FIG. 2 represents an example of an algorithm of operation of the safetymethod according to the invention.

Only the elements necessary for an understanding of the invention havebeen shown.

FIG. 1 represents schematically, the supply circuit for a heatingresistance 1 of a domestic iron composed of a soleplate in thermalcommunication with heating resistance 1 and a heel on which the iron canrest substantially vertically. Heating resistance 1 is connected inseries with a thermostat 2 whose assigned temperature is controlled bythe user and the supply circuit comprises two terminals L, N which aresubjected to a supply voltage when the iron is connected to theelectrical supply network.

In order to limit fire hazards, the iron is provided with a safetydevice composed of a safety relay 3 controlled by a control module 4,the safety relay 3 being mounted in series with heating resistance 1 sothat the opening of the safety relay 3 interrupts electric supply toheating resistance 1.

The control module 4 receives, in a manner known per se, informationfrom a motion detector 5 and a position sensor 6 making it possible todetermine if the iron rests or not on its heel. The position sensor 6 ispreferentially disposed to detect that the iron rests on its heel whilethe soleplate of the iron is tilted by more than 20° relative to thehorizontal. Thus, the iron is considered to be placed on its heel whenit is placed on an independent iron rest, such as the iron restintegrated into an ironing board, these iron rests generally having aninclination of about 45°. In an advantageous way, the control module 4is constituted by an ASIC or by an electronic circuit carried on aprinted circuit also supporting the whole of the other elements 3, 5, 6of the safety device.

More particularly according to the invention, the control module 4controlling the opening of the safety relay 3 incorporates or isconnected to means 2 a for determining the state of opening or closingof thermostat 2. As an example, these means 2 a determine the state ofopening of thermostat 2 by measuring the terminal voltage of a voltagedivider disposed between the heating element 1 and thermostat 2 or bymeasuring the current passing through the safety relay 3 using a shunt.

The safety device can thus control the opening of the safety relay 3 bytaking account of the state of opening of thermostat 2 so that theopening of the safety relay 3 can be carried out preferentially whenthermostat 2 is open. One thus avoids the accelerated wear of the safetyrelay 3 generated in particular by the appearance of electric arcs whenthe safety relay 3 is open when it is under tension.

A particular embodiment of the safety method for a domestic ironaccording to the invention now will be described in relation to FIG. 2.

According to this figure, in a first step 101 of the method, the controlmodule 4 determines if the iron is motionless, or immobile, usinginformation coming from the motion detector 5.

When the iron is regarded as motionless, the control module 4 carriesout step 102 of the method in which the control module 4 determines,with the assistance of the position sensor 6, whether the iron isimmobilized on its heel or its soleplate.

If the iron rests on its heel, the control module 4 passes then to step103A of the method in which it measures the time t that has elapsedsince the last moment to when the iron was determined to be motionless.This time t of immobilization of the iron is compared with apredetermined alarm threshold t_(1r), for example of about 8 minutes,then according to the result, the following operations are carried out:

if the elapsed time t is less than the alarm threshold t_(1r), themethod is returned to step 101. The control module 4 thus continues tomonitor the time t of immobilization of the iron and to compare it withthe threshold t_(1r).

if the time t of immobilization of the iron exceeds the alarm thresholdt_(1r), then the method passes to step 104A.

During step 104A, the control module 4 monitors the state of opening orclosing of thermostat 2 and carries out the following operations:

if thermostat 2 is in an open state, the control module 4 thenimmediately carries out step 106 of the method in which the controlmodule 4 controls the opening of the safety relay 3. Such an opening ofthe safety relay 3 is carried out when the latter is not traversed by acurrent so that the wear of the safety relay is extremely low.

inversely, when thermostat 2 is in a closed state, the control module 4carries out the intermediate step 105A of the method.

During step 105A, the control module 4 checks if the time t ofimmobilization of the iron exceeds a critical threshold t_(2r), longerthan the alarm threshold t_(1r). As an example, the value of thecritical threshold t_(2r) could be selected so that t_(2r)=t_(1r)+20seconds.

The control module 4 then carries out the following operations:

if the time t of immobilization of the iron does not exceed the value ofthe critical threshold t_(2r), the safety method is returned at step 101and control module 4 again carries out the operations associated withsteps 101 and following.

when the time t of immobilization of the iron exceeds the criticalthreshold t_(2r), the control module 4 immediately carries out step 106of the method in which the control module 4 controls the opening of thesafety relay 3. This opening of the safety relay 3 beyond the criticalthreshold t_(2r) of immobilization is carried out while the safety relayis under tension.

Once the opening of the safety relay 3 is carried out, the controlmodule 4 again carries out the various operations associated with steps101 and those that follow of the method.

In particular, if detector 5 detects a movement of the iron at the timeof step 101 of the method, the control module 4 then carries out thestep 110, which consists in controlling the closing of the safety relay3.

Lastly, if during step 102, the position sensor 6 sends to the controlmodule 4 the information according to which the iron is resting on itssoleplate, the control module 4 then carries out the steps 103B andthose that follow of the method. These steps 103B, 104B and 105B of themethod are on all points similar to the steps 103A, 104A and 105Apreviously described but with threshold values t_(1s) and t_(2s) inplace of the thresholds t_(1r) and t_(2r).

As an example, the alarm threshold t_(1s) is about 30 seconds and thecritical threshold t_(2s) is about 40 seconds so that the closing of thesafety relay 3 by the safety method intervenes much more quickly whenthe iron rests on its soleplate that when it rests on its heel.

Such a method of security of a domestic iron, by controlling the openingof the safety relay when the thermostat is in an open state over a rangeof immobilization time of the iron comprised between an alarm thresholdt_(1r), t_(1s) and a critical threshold t_(2r), t_(2s), has theadvantage of allowing in the majority of the cases the opening of thesafety relay when current is not flowing through this latter. Inparticular, when the iron rests a long time on its heel, the thermostatstarts to cycle rapidly so that the probability that the thermostat isfound in an open state over the range of time comprised between t_(1r)and t_(2r) is very high.

Such a safety method thus makes it possible to reduce the use of thesafety relay, which makes it possible to increase its lifespanconsiderably and thus to reduce the dimensioning of the relays. Thereresults a less expensive safety device.

In an advantageous manner, the safety method can also control theactivation of one or more indicators to inform the user when theimmobilization time of the iron exceeds the alarm threshold and thecritical threshold, respectively.

Of course, the invention is by no means limited to the embodimentdescribed and illustrated, which was given only as an example.Modifications remain possible, in particular from the point of view ofthe constitution of the various elements or by substitution of technicalequivalents, without leaving for all that the field of protection of theinvention.

Thus, in an alternative embodiment, the safety device could have onlyone sensor which, by an analysis of the signals, will make it possibleto determine at the same time the position of the iron and it beingplaced in movement. As an example, this sensor could be a sensorproviding a signal relating to the position of the iron, the detectionof movement of the iron being then carried out by obtaining the timederivative of the signal provided by this sensor.

Thus, in an alternative embodiment not represented, the invention couldalso be applied to a vertical smoothing appliance.

1. Ironing appliance composed of a heating element (1) controlled bymeans of a thermostat (2), the appliance being provided with a safetydevice comprising means for detection of movement (5) and a safety relay(3) assembled in series with the heating element (1) allowing tointerrupt the supply of power to said heating element (1) when theappliance remains motionless too long, wherein said safety devicecomprises means (2 a) for determining the state of opening of thethermostat (2) and the safety device controls the opening of said safetyrelay (3) when, simultaneously, the means (2 a) for determining indicatethat the thermostat (2) is open and the means for detection of movement(5) detect an immobilization of the appliance during a time t longerthan an alarm threshold t₁.
 2. Ironing appliance according to claim 1,wherein the safety device controls, at the latest, the opening of thesafety relay (3) when the appliance is motionless during a time t longerthan a critical threshold t₂, the critical threshold t₂ being longerthan the alarm threshold t₁.
 3. Ironing appliance according to claim 2,wherein the safety device monitors the state of the thermostat (2) whenthe time during which the appliance is motionless is comprised betweenthe alarm threshold t₁ and the critical threshold t₂ and controls theopening of the safety relay (3) as soon as the thermostat is detected tobe in an open state by the means (2 a) for determining the state ofopening.
 4. Ironing appliance according to claim 3, wherein it iscomposed of a heel on which it can rest during inactive phases ofironing and an ironing soleplate in thermal communication with theheating element, on which it can rest during active phases of ironing,the appliance comprising position detecting means (6) making it possibleto determine if the appliance rests or not on its heel and in thatvalues of the alarm threshold t₁ and the critical threshold t₂ are afunction of the position of the iron detected by the position detectingmeans (6).
 5. Ironing appliance according to claim 4, wherein the valuesof the alarm threshold t_(1r) and critical threshold t_(2r) when theiron rests on its heel are respectively longer than the values of thealarm threshold t_(1s) and critical threshold t_(2s) when the appliancerests on its soleplate.
 6. Safe operating method for an ironingappliance provided with a heating element (1) and a safety relay (3)disposed in series with the heating element (1), said method comprising:controlling supply of power to the heating element by means of athermostat (2); and opening the safety relay when the thermostat (2) isin an open state and the appliance remains motionless for a time tlonger than an alarm threshold t₁.
 7. Safe operating method according toclaim 6, wherein said step of opening the safety relay (3) is performed,at the latest, when the appliance remains motionless for a time t longerthan a critical threshold t₂, the critical threshold t₂ being longerthan the alarm threshold t₁.
 8. Safe operating method for an ironingappliance according to claim 7, wherein the state of opening of thethermostat (2) is monitored over a range of immobilization time of theappliance comprised between the alarm threshold t₁ and the criticalthreshold t₂ and the safety relay (3) is at opened as soon as thethermostat is detected in an open state in said range of immobilizationtime.
 9. Ironing appliance according to claim 2, wherein it is composedof a heel on which it can rest during inactive phases of ironing and anironing soleplate in thermal communication with the heating element, onwhich it can rest during active phases of ironing, the appliancecomprising position detecting means (6) making it possible to determineif the appliance rests or not on its heel and in that values of thealarm threshold t₁ and the critical threshold t₂ are a function of theposition of the iron detected by the position detecting means (6). 10.Ironing appliance according to claim 9, wherein the values of the alarmthreshold t_(1r) and critical threshold t_(2r) when the iron rests onits heel are respectively longer than the values of the alarm thresholdt_(1s) and critical threshold t_(2s) when the appliance rests on itssoleplate.
 11. Ironing appliance according to claim 1, wherein it iscomposed of a heel on which it can rest during inactive phases ofironing and an ironing soleplate in thermal communication with theheating element, on which it can rest during active phases of ironing,the appliance comprising position detecting means (6) making it possibleto determine if the appliance rests or not on its heel and in thatvalues of the alarm threshold t₁ and the critical threshold t₂ are afunction of the position of the iron detected by the position detectingmeans (6).
 12. Ironing appliance according to claim 11, wherein thevalues of the alarm threshold t_(1r) and critical threshold t_(2r) whenthe iron rests on its heel are respectively longer than the values ofthe alarm threshold t_(1s) and critical threshold t_(2s) when theappliance rests on its soleplate.